Dabney Gets Tanked
Saturday morning found Dabney in his garage tinkering with his 1965 Ford Fairlane 500. Its engine wasn't running smoothly, and Doctor Crankshaft was due any minute so that they could take the Fairlane out for a ride.
As Dabney was hooking up his dwell meter, Doc strolled up. "Hey Dabney. I thought we were gonna take this beauty for a spin. What'd you break now?"
"I didn't break anything, Doc. The engine isn't running right. It's always run perfectly but when I started it up this morning and drove it a couple blocks it died out. I restarted it and it died again after a couple blocks. That makes sense for a cold V8 engine from the 60s, but when it warmed up it still died. I figure the points might be a little oxidized and the dwell meter will give me the truth," said Dabney.
"Well, before you connect everything let's hear the engine," said the Doctor. Dabney started the car and, of course, it ran quite normally.
"Wow, that's pretty rough!" exclaimed the Doctor sarcastically. "Rev it up a little and see if it gets smoother."
Dabney revved the engine up to 2500 rpm and it ran fine for a couple minutes, after which it died.
"Hrumph," exclaimed the Doctor. "It sounds like fuel starvation more than electrical failure. Let's check the fuel pump pressure."
Dabney got out the vacuum gauge, which also doubles as a fuel pressure gauge. They disconnected the fuel line at the carburetor and pushed on the rubber hose from the gauge, then cranked the engine. "Odd, it's putting out a steady 4.5 pounds," said the Doctor.
Now things started getting interesting...
Doc raised an eyebrow and asked Dabney: "You do have a good amount of gas in the tank, don't you?"
"Yeah, yeah." Dabney was a little irritated at the obvious question. "You remember that rainy spell we had a couple of months ago when we got it hung up in the mud over at Charlies place. I had just filled it before we went over there and haven't driven it since. There's at least three-quarters of a tank in it."
"Oh, yeah," said the Doctor, "I have to admit you did a pretty good job of cleaning all that caked-on mud off the inner wheel wells and bottom of the car."
"It was horrible," said Dabney, "I had to take the wheels off to clean things well and the wire-spoked hubcaps took an hour to scrub. Do you think the mud had anything to do with this?"
"Maybe," said the Doctor, "But let's figure out why we're not getting good fuel siphoning from the tank to the pump. First, let's check the gas cap to make sure the vent hole isn't plugged up."
They unscrewed the gas cap and checked the vent hole. It was somewhat rusty, so the Doctor tried to blow some air through it. "This thing's pretty restricted, Dabney, maybe this is our problem," said the Doctor.
They cleaned off all the rust using a bench-mounted wire brush, then poked a thin wire through the hole to make sure it was clear. Afterwards they blew air through and it was far less restricted. To confirm that this might be the problem, before putting the cap back they ran the engine at 2500 rpm for ten minutes with no problems. They put the cap back on and drove the car, only to find the engine starving out after a few blocks.
"Now this is a fine kettle of fish," said Dabney. "I thought we had this problem licked."
"So did I," said the Doctor, "but if you think about it, that little vent hole in the cap isn't really so critical as to create a vacuum in the tank so quickly. The engine ran fine with the cap off. We need to find out what's causing the tank to develop a vacuum so fast. Let's go back to the garage"
When back at the garage, the Doctor insisted they put the car up on the lift. Once underneath the Doctor grabbed a utility light and started looking around. "What are you looking for, Doc?" asked Dabney.
"The other vent to this tank," said the Doctor. "These cars had vented gas caps alright, but in those days the manufacturers also put vent tubes in the systems to take care of vapor expansion as the tanks were filled. These vents also served to allow atmospheric pressure into the tanks for better siphoning to the engine. The darn things are really hidden well, though, and can be hard to find."
"Ahah!" exclaimed the Doctor. "There it is!" Behind the bumper, right next to a welded body flange, he found the vent tube. It was painted body color and hard to see, but there it was, complete with a cake of mud that had dried at its outlet.
"Well, Dabney, looks like you didn't quite get all the mud off the car," said the Doctor as he scraped the mud off the tube's end and cleaned out the opening with a screwdriver blade. "Now I bet this thing will take us wherever we want to go."
So they started out on their drive. "So, Dabney, where do you want to go?"
"I don't know, Doc, where do you want to go?"
"It's your car, Dabney, you pick."
"Yeah, but I invited you and you're my guest, you decide?" said Doc.
"No, no. It's not my decision," said Dabney. "You choose."
"Dabney..." said Doc. "Shut up and drive."